Field of the Invention
The present invention relates to a drive mechanism of an injection molding machine, and more particularly to a drive mechanism of an injection molding machine having an adjustment function of the shaft centers of a ball screw shaft and a motor shaft.
Description of the Related Art
An example of a configuration of a conventional injection molding machine will be described with reference to FIG. 4 and FIG. 5.
A movable plate 1 is supported by a guide member 2 to be movable in an axial direction. A ball screw nut 3 is fixed to this movable plate 1 in a manner such that it does not rotate, and a ball screw shaft 4 is engaged with the ball screw nut 3. This ball screw shaft 4 is supported by a rear plate 5 through a bearing 21, and is rotatable, but is unmovable in the axial direction. The ball screw shaft 4 thus configured is rotated, so that the ball screw nut 3 moves in the axial direction. Consequently, the movable plate 1 to which the ball screw nut 3 is fixed also moves.
The ball screw shaft 4 is rotationally driven by a ball screw driving motor 8. The ball screw driving motor 8 is fixed to the rear plate 5. A shaft of the driving motor 8 and the ball screw shaft 4 are coupled by a coupling member 6, so that torque of the driving motor 8 can be transmitted to the ball screw shaft 4.
In a ball screw drive mechanism of an injection molding machine, in a case where a ball screw shaft and a shaft of a ball screw driving motor are coupled with each other through a coupling member, the shaft center of ball screw shaft is preferably made to coincide with the shaft center of the motor shaft. In order to achieve this, it is necessary to improve the accuracy of the machining of each of a motor fixing part and a ball screw shaft fixing part. However, even when each machining accuracy is improved, it is necessary to provide a slight clearance in order to mount each member, and such a clearance could lead to deviation of the shaft centers.
As a conventional technology for solving such a problem, Japanese Patent Application Laid-Open No. 11-138599 discloses an in-line screw type electric injection molding machine in which a pair of injection motors are mounted on a rear surface of a pressure plate by using a bracket, respectively, and the output shafts of these motors are coupled to rear ends of ball screw shafts. Additionally, Japanese Patent Application Laid-Open No. 2013-984 discloses an injection apparatus in which the driving shaft center is aligned with the screw shaft center.
However, the above Japanese Patent Application Laid-Open No. 11-138599 discloses that the driving motor is fixed to the rear plate by means of the bracket, but does not disclose how to fix the bracket or does not disclose an adjustment mechanism for making the shaft center of the ball screw shaft coincide with the shaft center of the motor shaft.
Japanese Patent Application Laid-Open No. 2013-984, mentioned above, describes an adjustment mechanism for aligning the screw shaft center with the driving shaft center, wherein an adjustment protrusion is movable in an adjustment recess, but does not describe how to move the adjustment protrusion or how to adjust a slight deviation of the shaft centers.